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Electrical Systems Flashcards

6 cards from real DFFT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 6 Electrical Systems flashcards as text

  1. A vehicle's horn does not work. The fuse is intact. What should be tested next?

    Answer: The horn relay and the horn switch continuity

    After confirming the fuse is good, the relay and switch are the next most common failure points in a simple horn circuit.

  2. A vehicle's headlights flicker at idle but are steady at higher RPM. What is the most likely cause?

    Answer: Low alternator output at idle not meeting electrical demand

    Alternators produce less current at idle; if electrical demand exceeds output, voltage drops and lights may flicker until engine speed increases alternator output.

  3. During a DFFT electrical test, you find 0.8V voltage drop across a battery-to-starter cable under cranking load. Is this acceptable?

    Answer: No, maximum allowable voltage drop is typically 0.5V for high-current cables

    Excessive voltage drop in the starter cable reduces voltage available at the starter motor, causing slow cranking; maximum acceptable drop is typically 0.5V.

  4. A vehicle's battery goes flat overnight despite no obvious loads left on. What is this fault called?

    Answer: Parasitic drain or key-off current draw

    Parasitic drain refers to excessive current draw from a component that remains active after the ignition is off, slowly discharging the battery.

  5. What is the correct method to test for a parasitic drain on a vehicle?

    Answer: Connect an ammeter in series between the battery negative terminal and the cable

    An ammeter in series monitors the actual current flowing out of the battery with everything off, allowing the technician to identify which circuit is causing the drain.

  6. A vehicle's check engine light is on and a scan tool shows a P0300 random misfire code. What sensor data should be examined first?

    Answer: Live misfire counter data per cylinder and ignition system output

    Cylinder-specific misfire counters help pinpoint whether the misfire is truly random or concentrated in one cylinder, guiding diagnosis toward ignition, fuel, or mechanical causes.